In Routine§

See primary documentation in context for trait is raw

multi sub trait_mod:<is>(Routine:D $r:$raw!)

Gives total access to the data structure returned by the routine.

my @zipi = <zape zapatilla>;
sub þor() is raw {
    return @zipi
};
þor()[1= 'pantuflo';
say @zipi;  # OUTPUT: «[zape pantuflo]␤»